As St. Patrick's Day approaches, we are inundated with all things Irish, and because Guinness Stout is the quintessential Irish beer, we are also bombarded with all things Guinness.
One thing made with Guinness that is not Irish is the Black and Tan. Unless you have been living under a rock, a Black and Tan is beer cocktail made with half Guinness and half Bass Ale, where the Guinness floats on top of the Bass. This simple drink can be seen as a metaphor for many things Irish and English; they don't mix. An Irish folksong as case in point:
Come Out Ye Black and Tans
I was born on a Dublin street where the royal drums did beat
And the loving English feet walked all over us,
And every single night when me father'd come home tight
He'd invite the neighbors outside with this chorus:
(chorus) Oh, come out you black and tans,
Come out and fight me like a man
Show your wife how you won medals down in Flanders
Tell her how the IRA made you run like hell away,
From the green and lovely lanes in Killeshandra.
Although associated with St. Patrick's Day in the US as one of its two ingredients is Guinness, do not order a Black and Tan in Ireland.
Black and Tans is the nickname given to the British paramilitary force, largely made up of English WWI veterans, formed to suppress the Irish Independence movement in 1920 and 1921. The Black and Tans employed brutal tactics in an attempt suppress the Irish Republican Army's guerilla war, massacring civilians and burning Irish towns. They were called the "Black and Tans" due their khaki military trousers and darker police uniform shirts.
As a result of their mistreatment of the Irish people, Black and Tan is pejorative term in Ireland and calling someone a Black and Tan is an insult. Ordering a Black and Tan in a pub in Ireland with an American accent might not be taken as insult, but would certainly be considered quite culturally ignorant. To bring it back home, ordering a Black and Tan in today's Ireland would be like ordering a Red Coat in early 19th century America.
So this St. Patrick's Day, order a Half and Half instead. Similar to a Black and Tan, it is half Guinness Stout and half Harp Lager, making it all Irish.